Hydrochemical evolution of groundwater in northwestern part of the Indo-Gangetic Basin, India: A geochemical and isotopic approach
Shive Prakash, Kossitse Venyo Akpataku, Noble Jacob, Abhinav Patel, Suneel Kumar Joshi
Abstract
The present study aims to understand the hydrochemical evolution of groundwater in the Ghaggar River Basin, representing a zone of excessive abstraction of groundwater in the northwestern Indo-Gangetic Basin. The study comprises a regional scale and high-resolution sampling of groundwater during pre- and post-monsoon seasons of 2013 and their analyses for major ions, δ18O, δ2H, and 3H. Variation in hydrochemical and isotopic data is found both in spatial and vertical scales. The significant vertical variation of TDS, NO3- and K+ allowed the classification of the aquifer system into two major groups: shallow (depth < 80 m bgl) and deep (depth > 80 m bgl). The depth wise variations of δ18O and δ2H support this categorization of the aquifers. The Ca-HCO3 and Ca-Mg-Na-HCO3 water facies with higher values of 3H in the proximal part of the basin characterize recharge areas under humid conditions. The dominance of Mg-Na-HCO3 and Na-HCO3 facies in shallow and deep aquifers in central part of the basin, illustrate the intermediate to advanced stages of hydrochemical evolution in the system. Dominance of brackish Ca-Mg-Cl-SO4 and Na-Cl-SO4 water types in the discharge areas is due to the prevailing geological conditions and anthropogenic activities. Geochemical modelling supports the reverse cation exchange, mixing during lateral and vertical flow, weathering of silicate minerals, dissolution of crust salts, and evaporative enrichment are the natural processes governing the evolution of groundwater chemistry along the flow paths. The developed process-based conceptual model for the region will aid in the formulation of a suitable plan for groundwater resource management for a considerable period of time.